Chevy Impala Front Floorpan Replacement - Flooring It

At the rear righthand corner of the section we're replacing there was a small brace under the floor, attached by a couple of spot-welds. Using a spot-weld drill, these were removed to free the floorpan.

A dedicated spot-weld removal drill has a small point at its center, but is otherwise flat across the bottom. The point allows it to make its own center while drilling out a spot weld without damaging the panel underneath.

Our old, trusty, manually operated joggler was used to put a step in the new panel along what would be its rear-most edge. This was the only edge that wasn't butt- or plug-welded, and was only done this way to illustrate another method of joining panels. Normally we'd butt-weld the three sides that weren't plug welded. The step at the edge was welded over the old floorpan's edge, allowing the new sheetmetal to sit flush with the existing floor.

While most everyone knows to disconnect the battery when welding, here's a useful tip. If there's nowhere easily accessible to clamp the welder's ground cable to, it can be attached to a magnet as shown. Note the stepped joint in the foreground.

The same joint seen from below illustrates how it'll look factory once the welds are dressed and the floorpan is undercoated.

With most of the welds ground back, the floor is strong, watertight, and ready for another 40-plus years of service.

While the drill shown here is from Snap-on, and the cut-off wheel is a Clarke item, all the air tools to do this job are obtainable from Harbor Freight. Air-powered tools are smaller than their electric counterparts, and make jobs such as this so much easier. Of course you'll need a suitably sized compressor to run them too.

Here's the underfloor brace we referred to a while back, now plug-welded back in position. The lapped joint at the rear of the new panel can be seen here too.

Looking from underneath, the factory swage lines and stampings are as they should be, and an application of undercoating will see the repair as good as new.

Here you can see how well the new sheetmetal fits, butted against the original in the doorstep. It was tack-welded at first, before seam welding. Making the joint here on the curved section made grinding it flush easier later.

Here's the plug-welded lap joint at the base of the toeboard. The spot-weld drill was used to perforate the new panel prior to fitment.